Major difficulties are often encountered when balancing heavy rotary members such as motor vehicle wheels, for example for trucks, tractors and the like, more especially when the wheel has to be mounted on to the measuring spindle of a balancing machine and when the wheel has to be clamped on to the appropriate clamping arrangement on the measuring spindle of the machine. In specific terms, in that procedure the wheel must be raised to the level of the measuring spindle and aligned with respect to the measuring spindle or the clamping device thereon, so that the longitudinal center lines of the wheel and the measuring spindle are in alignment with each other, whereupon the wheel has to be moved on to the measuring spindle to be clamped thereon.
One form of apparatus for positioning a rotary member on a balancing machine having a measuring spindle, in such a way that the rotary member can be lifted into a position at the level of the measuring spindle of the balancing machine, as disclosed for example in German laid-open application (DE-OS) No. 20 05 980, comprises for example a lift carriage with a steerable frame which can be raised and lowered by means of a preferably hydraulically actuated lifting device and which has two horizontally extending fork arms which are connected by way of a transverse bearer. At least one support roller is associated with each fork arm. The fork arms can be moved under the wheel which is to be fitted in position, being disposed in an upright position, whereupon the wheel can be supported against the support rollers, raised in the upright position to the fitment height therefor and moved into the fitting position by an axial turning movement. Such an arrangement is very similar to wheel fitting lifting carriages or wheel lifters for replacing wheels on motor vehicles.
Another form of apparatus, as described in German patent specification No. 1 480 858, comprises a movable mounting unit for heavy motor vehicle wheels with a tire fitted thereon. That mounting unit, which is extremely expensive, comprises a generally fork-shaped base frame structure which is provided with vertically extending guideways and which can also be moved into a position under the wheel to be picked up thereby, similarly to the apparatus described above and as disclosed in German laid-open application No. 20 05 980. The mounting unit further comprises a wheel receiving arrangement with mounting members which are arranged movably on the guideways of the base frame structure, and horizontal support arms for the wheel to be picked up, the support arms being integrally connected to the above-mentioned mounting members and extending between first and second fork arms of the forked base frame structure on respective sides of the wheel. The mounting unit further includes a lifting device for lifting the entire wheel receiving arrangement. The mounting unit additionally includes upper yoke members carrying rollers which run on the rear sides of the vertical guideways, handles which are carried by the yoke members and which are connected to the vertical support members of the wheel receiving arrangement, lower rollers which are also carried by the vertical support members but which run at the front sides of the vertical guideways, and a holding assembly for setting the upper yoke members at the desired angular position.
Another form of wheel lifting device which is especially suitable for a balancing machine is to be found for example in German utility model No. 17 78 921. That assembly has lift supports of a lifting unit, and arranged on the lift supports is a wheel receiving arrangement which is mounted pivotably in the lift supports by means of a mounting pin and has a horizontal member for receiving the wheel, an angular member, a holding member for securing the wheel in its respective position, and a curved support member. While that configuration, unlike the above-described prior apparatuses, is of a comparatively simple structure, it also suffers from the disadvantage that positioning the wheel at the balancing machine involves major problems.